Blender 2.49b: Loop animation between selected markers
The options I was looking for were indeed trivial. Nor did the pose markers have anything to do with the looping.

On the Timeline window, select "Frame" menu, followed by "Set as Start (Shift s)". This merely means that if the animation starts before this point, it will advance normally until the end point, following which it will loop in-between the current start and end points.

One can see the start and end points in the image in the OP by noting the section of light gray in the timeline window (Which also happens to match up with the pose markers, implying that they have something to do with the looping; they don't.)